Like other people, we noticed overheating issues as soon as summer kicked off. It was basically unusable in our office, which only gets to 76F or so.
We’re in an old building without AC, and I suspect a lot of sheds and garages have the same issue.
So, this is a $300 solution, but it’s bulletproof (and also cools down our office a bit).
We bought a $280 portable AC from Home Depot along with two cheap ($20) wire rack shelves. The AC fits perfectly underneath and between the two shelves, and we cut vent holes in a piece of plexiglass for the two vents.